yes the place where you remove the cap to get to the dipstick is where you fill it.
also you need to make sure the forks are on the ground before you check it.
then when you look at the dipstick you should see 3 marks labeled H, N and L.
H = high level
N = Normal level
L = Low level
you want the oil to be at least to the N mark but no higher than the H mark when the oil is hot.
As for the type of oil? mitsubitshi uses SAE5 or SAE10 weight oil. Their recommended brands to use are Essolube D3 10wt, Mobil DTE24 or 26, and Shell Telus Oil 25 or 33. Our shop used AW32 though and had no problems out of it. AW32 replaces most 10wt hydraulic oils that were used in the past.

hope this helps